Sheet aligning mechanism

ABSTRACT

A sheet aligning mechanism includes first and second conveyance mechanisms disposed on first and second sides of a sheet conveyance path, respectively. A nip is formed between the first and second conveyance mechanisms. The first conveyance mechanism includes a first roller, a second roller, and a first conveyance belt wound around the first and second rollers. The first and second rollers are configured to rotate in a first direction along a sheet conveying direction for sheet conveyance, and stop rotation or rotate in a second direction opposite to the first direction for sheet alignment. The first conveyance belt includes an extended region between the first and second rollers in an extending direction inclined with respect to the sheet conveying direction, such that a width of the sheet conveyance path becomes narrower towards the nip in the sheet conveying direction.

FIELD

Embodiments described herein relate generally to a sheet aligningmechanism and an image forming apparatus.

BACKGROUND

An image forming apparatus includes a sheet aligning mechanism forcorrecting an inclination of a sheet. The sheet aligning mechanismaligns the sheet to correct the inclination of the sheet by causing aleading end of the sheet to be aligned with a nip of rollers (aligningrollers). The sheet aligning mechanism conveys the sheet by driving therollers after aligning.

However, when the sheet is too thick, the sheet aligning mechanism maynot properly convey the sheet after aligning.

DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an overview of an image forming system including animage forming apparatus according to an embodiment.

FIG. 2 illustrates a schematic side view of a conveyance unit includinga sheet aligning mechanism.

FIG. 3 illustrates a perspective view of the sheet aligning mechanism.

FIG. 4 illustrates an enlarged side view of the sheet aligningmechanism.

FIG. 5 illustrates a schematic side view of a part of a conveyance unitincluding a sheet aligning mechanism according to a comparative example.

FIG. 6 illustrates an enlarged side view of the sheet aligning mechanismaccording to the comparative example.

FIG. 7 illustrates a perspective view of a sheet aligning mechanismaccording to a first modification of the embodiment.

FIG. 8 illustrates a schematic side view of a sheet aligning mechanismaccording to a second modification of the embodiment.

FIG. 9 illustrates a schematic side view of a sheet aligning mechanismaccording to a third modification of the embodiment.

DETAILED DESCRIPTION

In general, according to an embodiment, a sheet aligning mechanismincludes a first conveyance mechanism disposed on a first side of asheet conveyance path and a second conveyance mechanism disposed on asecond side of the sheet conveyance path opposite to the first side. Anip is formed between the first and second conveyance mechanisms. Thefirst conveyance mechanism includes a first roller, a second roller, anda first conveyance belt wound around the first and second rollers. Thefirst and second rollers are configured to rotate in a first directionalong a sheet conveying direction for sheet conveyance, and stoprotation or rotate in a second direction opposite to the first directionfor sheet alignment. The first conveyance belt includes an extendedregion between the first and second rollers in an extending directioninclined with respect to the sheet conveying direction, such that awidth of the sheet conveyance path becomes narrower towards the nip inthe sheet conveying direction.

Hereinafter, a sheet aligning mechanism and an image forming apparatusaccording to an embodiment will be described with reference to thedrawings. In each drawing, the same reference numerals are used for thesame components. In each drawing, a dimension and a shape of eachelement may be exaggerated or simplified for easy understanding.

FIG. 1 illustrates an overview of an example of an image forming system1. As illustrated in FIG. 1, the image forming system 1 includes animage forming apparatus 2 and a post-processing apparatus 3. The imageforming apparatus 2 forms an image on a sheet. The post-processingapparatus 3 performs post-processing on the sheet conveyed from theimage forming apparatus 2.

The image forming apparatus 2 includes a control panel 11, a scannerunit 12, a printer unit 13, a paper feed unit 14, a paper discharge unit15, and an image forming control unit 16.

The control panel 11 includes various keys to receive an operation of auser. For example, the control panel 11 receives an input related to atype of post-processing of a sheet. The control panel 11 transmitsinformation regarding the type of the post-processing to thepost-processing apparatus 3.

The scanner unit 12 includes a reading unit to obtain image informationof an object to be copied. The scanner unit 12 transmits the imageinformation to the printer unit 13.

The printer unit 13 forms an output image (hereinafter, referred to as a“toner image”) by using developer such as toner, based on the imageinformation transmitted from the scanner unit 12 or an external device.The printer unit 13 transfers the toner image on a surface of the sheet.The printer unit 13 fixes the toner image onto the sheet by applyingheat and pressure on the toner image transferred on the sheet.

The paper feed unit 14 supplies sheets to the printer unit 13 one by one(or one copy) according to a timing when the printer unit 13 forms thetoner image.

The paper discharge unit 15 conveys the sheet discharged from theprinter unit 13 to the post-processing apparatus 3.

The image forming control unit 16 controls an overall operation of theimage forming apparatus 2. That is, the image forming control unit 16controls the control panel 11, the scanner unit 12, the printer unit 13,the paper feed unit 14, and the paper discharge unit 15. The imageforming control unit 16 may be formed of a control circuit including aCPU, a ROM, and a RAM.

The post-processing apparatus 3 is disposed adjacent to the imageforming apparatus 2. The post-processing apparatus 3 executespost-processing specified through the control panel 11, on the sheetconveyed from the image forming apparatus 2. For example, thepost-processing is stapling or sorting.

Hereinafter, a conveyance unit will be described. FIG. 2 illustrates aschematic side view of a conveyance unit 30. As illustrated in FIG. 1,the image forming apparatus 2 includes the conveyance unit 30(conveyance device, see FIG. 2). The image forming apparatus 2 includesa conveyance path 31 (see FIG. 2) for conveying a sheet S.

The sheet S (object to be conveyed) maybe one sheet (for example, normalpaper), or may be a layered body in which a plurality of sheets overlapone another. The layered body may include a sealed letter, a clear file,an envelope, a label seal, or the like. For example, the layered body isformed by folding one or more sheets . For example, the sealed letterincludes an envelope and one or more sheets put into the envelope.

As illustrated in FIG. 2, the conveyance unit 30 includes a conveyancepath forming unit 38, a sheet aligning mechanism 40, and a pair ofconveyance rollers 71 and 72. The sheet S is conveyed substantially fromthe bottom to the top along the conveyance path 31. The sheet S isconveyed from the paper feed unit 14 (for example, a paper feedcassette) to the printer unit 13 (for example, an image forming unit)through the conveyance unit 30 (see FIG. 1) . The side of the paper feedunit 14 (lower side in the paper face of FIG. 2) in a conveyancedirection Vs of the sheet S is referred to as an “upstream side . ” Theside of the printer unit 13 (upper side in the paper face of FIG. 2) inthe conveyance direction Vs is referred to as a “downstream side.” Adirection V1 (a depth direction in the paper face of FIG. 2)perpendicular to the conveyance direction Vs in the surface of the sheetS conveyed along the conveyance path 31 is referred to as a “conveyanceperpendicular direction V1” (see FIG. 3) .

The conveyance path forming unit 38 forms the conveyance path 31 betweenthe paper feed unit 14 (see FIG. 1) and the printer unit 13 (see FIG. 1). The conveyance path forming unit 38 forms a bending space 39 of thesheet S on the upstream side of a pair of conveyance mechanisms 41 and42. FIG. 2 illustrates a state where the sheet S bends in the bendingspace 39 after the leading end of the sheet S collides with the pair ofconveyance mechanisms 41 and 42.

Hereinafter, the sheet aligning mechanism will be described. Asillustrated in FIG. 2, the sheet aligning mechanism 40 includes the pairof conveyance mechanisms 41 and 42, an aligning motor 43, and a controlunit 70. The pair of conveyance mechanisms 41 and 42 are providedbetween the pair of conveyance rollers 71 and 72 and the printer unit 13(see FIG. 1) in the conveyance direction Vs.

FIG. 3 illustrates a perspective view of the sheet aligning mechanism.FIG. 4 illustrates an enlarged side view of the sheet aligningmechanism. As illustrated in FIG. 3, the pair of conveyance mechanisms41 and 42 include a first conveyance mechanism 41 and a secondconveyance mechanism 42. The sheet aligning mechanism 40 aligns aposition of the leading end of the sheet S by causing the sheet Sconveyed along the conveyance path 31 to collide with the pair ofconveyance mechanisms 41 and 42. The position of the leading end of thesheet S means a position of a downstream end of the sheet S in theconveyance direction Vs.

The first conveyance mechanism 41 includes a pair of support rollers 51and 52 (first support rollers), and a first conveyance belt 53. Thesupport roller 51 is provided on a rotary shaft 46. The support roller51 extends in the conveyance perpendicular direction V1. The aligningmotor 43 (see FIG. 2) rotates the support roller 51 by rotating therotary shaft 46. The support roller 52 is provided on a rotary shaft 47.The rotary shaft 47 extends in parallel with the rotary shaft 46. Thesupport roller 52 is provided on the downstream side of the conveyancedirection Vs with respect to the support roller 51. The support roller52 is spaced apart from the support roller 51. The support roller 52 ispositioned such that the first conveyance belt 53 can contact a secondconveyance belt 63. The support roller 52 is arranged in parallel withthe support roller 51.

The first conveyance belt 53 is an endless belt. The first conveyancebelt 53 is wound around the outer circumference of the support roller 51and the outer circumference of the support roller 52. The firstconveyance belt 53 faces the second conveyance belt 63 of the secondconveyance mechanism 42. The first conveyance belt 53 is rotatedaccording to the rotation of the support roller 51. The first conveyancebelt 53 is made of rubber (ethylene propylene diene rubber, or thelike), resin, or the like.

A first facing portion 54 is a portion of the first conveyance belt 53that bridges between the support rollers 51 and 52. An outer surface ofthe first facing portion 54 is a first facing surface 55. The firstfacing surface 55 is planar and faces the conveyance path 31. The firstfacing surface 55 inclines in a direction to approach the conveyancepath 31 toward the conveyance direction Vs. For example, an inclinationangle θ1 (can be also referred to as approach angle) (see FIG. 4) of thefirst facing surface 55 with respect to the conveyance path 31 isgreater than 0°. For example, the inclination angle θ1 is in a range of10° to 45°. For example, the outer surface of the first conveyance belt53 (for example, the first facing surface 55) contacts the sheet S whenaligning, and aligns the position of the leading end of the sheet S.

As illustrated in FIG. 4, the first conveyance mechanism 41 may changeits angle with respect to the conveyance path 31, i.e., the inclinationangle θ1 of the first facing surface 55. For example, the firstconveyance mechanism 41 may pivot about an axis line of a center axis ofthe support roller 52. For example, the first conveyance mechanism 41pivots about the center axis of the support roller 52 as the axis line,such that the first conveyance mechanism 41 can be at a certain angleposition between a first position P1 indicated by solid lines, and asecond position P2 indicated by imaginary lines. The inclination angleof the first facing surface 55 in the second position P2 is larger thanthe inclination angle of the first facing surface 55 in the firstposition P1. The first conveyance mechanism 41 may be changed in itsangle position by a driving unit (not illustrated) such as a motor.

As illustrated in FIG. 3, the second conveyance mechanism 42 is arrangedto face the first conveyance mechanism 41. The second conveyancemechanism 42 nips the sheet S with the first conveyance mechanism 41(specifically, the first conveyance belt 53) to convey the sheet. Thesecond conveyance mechanism 42 includes a pair of support rollers 61 and62 (second support rollers), and a second conveyance belt 63. Thesupport roller 61 is provided on a rotary shaft 56. The support roller61 extends in the conveyance perpendicular direction V1. The supportroller 62 is provided on a rotary shaft 57. The rotary shaft 57 extendsin parallel with the rotary shaft 56. The support roller 62 is providedon the downstream side of the conveyance direction Vs with respect tothe support roller 61. The support roller 62 is spaced from the supportroller 61. The support roller 62 arranges the second conveyance belt 63to be able to contact the first conveyance belt 53. The support roller62 is arranged in parallel with the support roller 61.

The second conveyance belt 63 is an endless belt. The second conveyancebelt 63 is wound around the outer circumference of the support roller 61and the outer circumference of the support roller 62. The secondconveyance belt 63 faces the first conveyance belt 53 of the firstconveyance mechanism 41. The second conveyance belt 63 is rotatedaccording to the first conveyance belt 53. The second conveyance belt 63is made of rubber (ethylene propylene diene rubber, or the like), resin,or the like.

A second facing portion 64 is a portion of the second conveyance belt 63that extends between the support rollers 61 and 62. An outer surface ofthe second facing portion 64 is a second facing surface 65. The secondfacing surface 65 is planar and faces the conveyance path 31. The secondfacing surface 65 inclines in a direction to approach the conveyancepath 31 toward the conveyance direction Vs. For example, an inclinationangle θ2 (can be also referred to as approach angle) (see FIG. 4) of thesecond facing surface 65 with respect to the conveyance path 31 isgreater than 0°. For example, the inclination angle θ2 is in a range of10° to 45°. The second facing surface 65 faces the first facing surface55. The outer surface of the second conveyance belt 63 (for example, thesecond facing surface 65) contacts the sheet S along with the outersurface of the first conveyance belt 53 when aligning, and aligns theposition of the leading end of the sheet S.

The first conveyance belt 53 and the second conveyance belt 63 contacteach other, thereby forming the nip 44. In the first conveyancemechanism 41 and the second conveyance mechanism 42, the sheet S isnipped between the first conveyance belt 53 and the second conveyancebelt 63 to be conveyed.

As illustrated in FIG. 4, the second conveyance mechanism 42 may changeits angle position, i.e., the inclination angle θ2 of the second facingsurface 65. For example, the second conveyance mechanism 42 may pivotabout a center axis of the support roller 62 as the axis line. Forexample, the second conveyance mechanism 42 pivots about the axis lineof the center axis of the support roller 62, such that the secondconveyance mechanism 42 can have a certain angle position between afirst position P3 indicated by solid lines, and a second position P4indicated by imaginary lines. The inclination angle of the second facingsurface 65 in the second position P4 is larger than the inclinationangle of the second facing surface 65 in the first position P3. Thesecond conveyance mechanism 42 may be changed in its angle position by adriving unit (not illustrated) such as a motor.

Since the first conveyance mechanism 41 and the second conveyancemechanism 42 can change their angle positions as described above, theinclination angles θ1 and θ2 of the facing surfaces 55 and 65 can beadjusted according to thickness of the sheet S. For example, as thesheet S is thicker, the inclination angles θ1 and θ2 can be made larger.

The first conveyance mechanism 41 and the second conveyance mechanism 42may change their angle positions independently from each other.Accordingly, the first conveyance mechanism 41 and the second conveyancemechanism 42 can adjust the inclination angles θ1 and θ2 independentlyfrom each other.

As illustrated in FIG. 2, the sheet S may bend in the bending space 39.In this case, the sheet S may incline with respect to the conveyancepath 31 and may enter between the pair of conveyance mechanisms 41 and42 . The pair of conveyance mechanisms 41 and 42 can adjust theinclination angles θ1 and θ2 (see FIG. 4) of the facing surfaces 55 and65 according to a bending shape of the sheet S in the bending space 39.For example, as illustrated in FIG. 4, the facing surfaces 55 and 65 maymake one of the inclination angles θ1 and θ2 larger relatively to theother one. Specifically, when the sheet S bends toward the firstconveyance mechanism 41, the sheet S may enter between the pair ofconveyance mechanisms 41 and 42 diagonally from above in FIG. 4.Therefore, the inclination angle θ1 of the first facing surface 55 maybe made larger in comparison to the inclination angle θ2 of the secondfacing surface 65. As a result, the sheet S can be more reliablyintroduced between the pair of conveyance mechanisms 41 and 42.

As illustrated in FIG. 3, the support roller 51 of the first conveyancemechanism 41 rotates in the clockwise direction (a direction indicatedby the arrow R1 of FIG. 3) (forward rotation) when letting the sheet Sadvance toward the nip 44. The first conveyance mechanism 41 stops orrotates in the counter clockwise direction (direction indicated by thearrow R2 of FIG. 3) (reverse rotation) when aligning, that is, when thesheet S collides with the pair of conveyance mechanisms 41 and 42.

The control unit 70 (see FIG. 2) may adjust the inclination angles θ1and θ2 of the first facing surface 55 and the second facing surface 65(see FIG. 4) by controlling a driving force of the driving unit. Forexample, when driving the pair of conveyance mechanisms 41 and 42 afteraligning, the control unit 70 may change the angle positions of the pairof conveyance mechanisms 41 and 42, such that the inclination angles θ1and θ2 are made smaller compared to those when aligning.

In the process of correcting the inclination of the sheet S whenaligning, the sheet S may slip sideways in a state of being in contactwith the conveyance belts 53 and 63. The sideslip means that the sheet Sslips in the conveyance perpendicular direction V1. If the inclinationangles θ1 and θ2 are relatively large when aligning, contact lengths(for example, contact lengths L1 and L2 of FIG. 4) of the sheet S withthe facing surfaces 55 and 65 become shorter. Therefore, frictionsbetween the sheet S and the facing surfaces 55 and 65 are reduced, andthe sideslip is more likely to occur. Accordingly, the inclination ofthe sheet S is sufficiently corrected.

If the inclination angles θ1 and θ2 are made smaller after aligning, acontact angle of the sheet S with the facing surfaces 55 and 65 (forexample, a contact angle α1 of FIG. 4) becomes smaller, and thus aconveying resistance when the pair of conveyance mechanisms 41 and 42convey the sheet S is reduced. In addition, if the inclination angles θ1and θ2 are made smaller, the contact lengths of the sheet S with thefacing surfaces 55 and 65 become longer. Therefore, a conveyance forcewhen the pair of conveyance mechanisms 41 and 42 convey the sheet Sincreases. Accordingly, when the pair of conveyance mechanisms 41 and 42convey the sheet S after aligning, the sheet conveyance capability canbe improved.

As illustrated in FIG. 2, the pair of conveyance rollers 71 and 72 areprovided at a position on the upstream side of the sheet aligningmechanism 40 in the conveyance direction Vs. The pair of conveyancerollers 71 and 72 include a first conveyance roller 71 and a secondconveyance roller 72 which face each other. The first conveyance roller71 is driven by a motor 73. The second conveyance roller 72 is rotatedaccording to the rotation of the first conveyance roller 71 (follow-uprotation). The pair of conveyance rollers 71 and 72 convey the sheet Stoward the downstream side of the conveyance path 31.

A conveyance guide 58 illustrated in FIG. 3 guides the sheet S betweenthe pair of conveyance mechanisms 41 and 42.

Hereinafter, a movement of a sheet in aligning will be described. First,aligning in a sheet aligning mechanism according to a comparativeexample will be described.

FIG. 5 illustrates a schematic side view of a part of a conveyance unitincluding a sheet aligning mechanism according to a comparative example.FIG. 6 illustrates an enlarged side view of the sheet aligning mechanismaccording to the comparative example. As illustrated in FIG. 5, thesheet aligning mechanism 140 of the comparative example includes a pairof registration rollers 141 and 142, instead of the first conveyancemechanism 41 and the second conveyance mechanism 42, respectively (seeFIG. 3). A pick-up roller 151 conveys a sheet in the paper feed unit 14(see FIG. 1) to a paper feed roller 152. The paper feed roller 152conveys the sheet to a conveyance path 131. A separation roller 153returns a sheet unintendedly taken out to the paper feed unit 14 (seeFIG. 1). An aligning guide 154 guides the sheet to the pair ofregistration rollers 141 and 142. In aligning, a leading end of thesheet collides with the pair of registration rollers 141 and 142. As aresult, the pair of registration rollers 141 and 142 correct theinclination of the sheet.

As illustrated in FIG. 6, if the sheet S is thick, an angle a2 formed bytangential lines T3 and T4 from contact positions between the sheet Sand the pair of registration rollers 141 and 142 increases. Therefore, aconveyance resistance when the pair or registration rollers 141 and 142convey the sheet S increases. If the sheet S is thick, contact lengthsL3 and L4 of the sheet S with the pair of registration rollers 141 and142 become short. Therefore, a conveyance force when the pair ofregistration rollers 141 and 142 convey the sheet S is reduced.Accordingly, when the pair of registration rollers 141 and 142 conveythe sheet S after aligning, the sheet conveyance capability may beinsufficient.

Hereinafter, aligning in the sheet aligning mechanism according to anembodiment will be described.

As illustrated in FIG. 4, in aligning by using the sheet aligningmechanism 40 of an embodiment, the leading end of the sheet S contactsthe facing surfaces 55 and 65 of the pair of conveyance mechanisms 41and 42. In this case, the conveyance belts 53 and 63 may stop or may bereversely rotated. The leading end of the sheet S contacts the facingsurfaces 55 and 65, such that the leading end of the sheet S is parallelwith the conveyance perpendicular direction V1 (see FIG. 3) .Accordingly, the conveyance belts 53 and 63 align the position of theleading end of the sheet S. That is, the inclination of the sheet S iscorrected.

After aligning, the pair of conveyance mechanisms 41 and 42 are drivenand the sheet S is conveyed in the conveyance direction Vs. Since thefirst conveyance mechanism. 41 and the second conveyance mechanism 42include two support rollers, respectively, the first facing portion 54and the second facing portion 64 include sufficient lengths.Accordingly, even if the sheet S is thick, the sheet S can contact thefacing surfaces 55 and 65 of the conveyance belts 53 and 63. If theinclination angles θ1 and θ2 are small, the angle α1 (contact angle α1)formed by tangential lines T1 and T2 from contact positions between thesheet S and the pair of facing surfaces 55 and 65 is smaller incomparison to the contact angle α2 (see FIG. 6) in the comparativeexample. Accordingly, the conveyance resistance when the pair ofconveyance mechanisms 41 and 42 conveys the sheet S is reduced. Inaddition, if the inclination angles θ1 and θ2 are small, the contactlengths L1 and L2 of the sheet S with the facing surfaces 55 and 65become long. Therefore, the conveyance force when the pair of conveyancemechanisms 41 and 42 convey the sheet S increase . Accordingly, when thepair of conveyance mechanisms 41 and 42 convey the sheet S afteraligning, the sheet conveyance capability can be improved. As a result,even if the sheet S is thick, a conveyance defect may not occur. Inaddition, if the sheet S is normal paper, a conveyance delay which maybe caused by a conveyance slip can be suppressed.

Hereinafter, modifications will be described.

FIG. 7 illustrates a perspective view of a sheet aligning mechanism 240according to a first modification of the embodiment. As illustrated inFIG. 7, the sheet aligning mechanism 240 differs from the sheet aligningmechanism 40 illustrated in FIG. 3 in that the sheet aligning mechanism240 includes a first conveyance mechanism 241 instead of the firstconveyance mechanism 41 (see FIG. 3).

The first conveyance mechanism 241 includes the support rollers 51 and52, and a first conveyance belt 253. The first conveyance belt 253includes a middle region 81 (first region) and end regions 82 and 82(second regions). For example, the middle region 81 is a region thatincludes a middle portion of the first conveyance belt 253 in conveyanceperpendicular direction V1. The middle region 81 is a belt-shaped regionthat stretches the full length of the first conveyance belt 253. The endregions 82 and 82 are regions that are disposed on end sides of thesupport rollers 51 and 52 with respect to the middle region 81. The endregions 82 and 82 are adjacent to one side and the other side of themiddle region 81 in the conveyance perpendicular direction V1. The endregions 82 and 82 are belt-shaped regions stretching the full length ofthe first conveyance belt 253.

The outer surface of the middle region 81 has a first frictioncoefficient μ1 with respect to the sheet S in the conveyance directionVs. The outer surfaces of the end regions 82 and 82 have a secondfriction coefficient μ2 with respect to the sheet S in the conveyancedirection Vs. The second friction coefficient μ2 is lower than the firstfriction coefficient μ1. The friction coefficients μ1, μ2 are staticfriction coefficients or dynamic friction coefficients. A method ofmeasuring the static friction coefficient and the dynamic frictioncoefficient is disclosed in ASTM D1894, for example.

The end (end in the conveyance perpendicular direction V1) of the sheetis more likely to contact the end regions 82 and 82 when aligning. Whenthe inclination of the sheet S is corrected, the end of the sheet S mayslip sideways in a state of being in contact with the conveyance belts253 and 63.

Since the friction coefficient μ2 of the end regions 82 and 82 is lowerthan the friction coefficient μ1 of the middle region 81, the sideslipof the sheet S is more likely to occur in the sheet aligning mechanism240. Accordingly, the inclination of the sheet S can be sufficientlycorrected.

FIG. 8 illustrates a schematic side view of a sheet aligning mechanism340 according to a second modification of the embodiment. As illustratedin FIG. 8, the sheet aligning mechanism 340 differs from the sheetaligning mechanism 40 illustrated in FIG. 3 in that the sheet aligningmechanism 340 includes a first conveyance mechanism 341 instead of thefirst conveyance mechanism 41 (see FIG. 3).

The first conveyance mechanism 341 includes the support rollers 51 and52, and a first conveyance belt 353. An outer surface of a first facingportion 354 of the first conveyance belt 353 is a first facing surface355.

The first conveyance belt 353 includes a first region 381 and a secondregion 382 . The first region 381 and the second region 382 differ fromeach other in positions in the length direction (circumferentialdirection) of the first conveyance belt 353. The outer surface of thefirst region 381 has a first friction coefficient μ3 with respect to thesheet S in the conveyance direction Vs. The outer surface of the secondregion 382 has a second friction coefficient μ4 with respect to thesheet S in the conveyance direction Vs. The first friction coefficientμ3 and the second friction coefficient μ4 differ from each other. Forexample, the first friction coefficient μ3 is lower than the secondfriction coefficient μ4. The friction coefficients μ3, μ4 are staticfriction coefficients or dynamic friction coefficients.

The first conveyance belt 353 is arranged such that the sheet S contactsa region (for example, the first region 381) of the regions 381 and 382that has a low friction coefficient when being aligned. For example, thefirst region 381 is arranged to face the conveyance path 31. Because ofthis arrangement, the sideslip of the sheet S is more likely to occur.Accordingly, the inclination of the sheet S can be sufficientlycorrected. Since the first conveyance belt 353 includes the region of ahigh friction coefficient (for example, the second region 382), theconveyance force when the conveyance mechanisms 341 and 42 convey thesheet S after aligning is not reduced that much.

Although both the first conveyance mechanism 41 and the secondconveyance mechanism. 42 in the sheet aligning mechanism 40 illustratedin FIG. 3 include the support rollers and the conveyance belts,respectively, the sheet aligning mechanism may be configured such thatonly one of the first conveyance mechanism and the second conveyancemechanism includes the support rollers and the conveyance belt.

FIG. 9 illustrates a schematic side view of a sheet aligning mechanism440 according to a third modification of the embodiment. As illustratedin FIG. 9, the sheet aligning mechanism 440 differs from the sheetaligning mechanism 40 illustrated in FIG. 3 in that a conveyance roller442 (second conveyance mechanism) is used instead of the secondconveyance mechanism 42 (see FIG. 3). The conveyance roller 442 isarranged to face the first conveyance mechanism 41. The conveyanceroller 442 is provided on a rotary shaft 456 which extends in parallelwith the rotary shafts 46 and 47. The conveyance roller 442 extends inthe conveyance perpendicular direction V1 (see FIG. 3). The firstconveyance belt 53 and the conveyance roller 442 contact each other toform a nip 444. The conveyance roller 442 nips the sheet S with thefirst conveyance mechanism 41 (specifically, the first conveyance belt53) to convey the sheet S. The conveyance roller 442 may be made of, forexample, rubber, resin, metal, or the like. If the conveyance roller 442is made of metal (stainless steel, aluminum, or the like), the abilityto remove static electricity can be enhanced. The sheet aligningmechanism 440 has a simple structure, and thus can be miniaturized.

The installation position of the sheet aligning mechanism 40 illustratedin FIG. 2 is not limited to between the paper feed unit 14 and theprinter unit 13 (see FIG. 1). The conveyance unit 30 (see FIG. 2) may beprovided at any position of the conveyance path in the image formingsystem (image forming apparatus, post-processing apparatus).

The number of support rollers forming one conveyance mechanism is notlimited to 2, and the number may be a certain number larger than orequal to 2. For example, the conveyance mechanism may include three ormore support rollers arranged in parallel with one another, and aconveyance belt wound around the three or more support rollers.

According to at least one embodiment described above, the inclinationangle of the first facing surface can be made small, and thus thecontact angle between the sheet and the first facing surface can be madesmall. Therefore, the conveyance resistance when the first conveyancemechanism and the second conveyance mechanism convey the sheet can bereduced. Since the sheet aligning mechanism of the embodiment can makethe inclination angle of the first facing surface small, the contactlength of the sheet with the first facing surface increases. Therefore,the conveyance force when the first conveyance mechanism and the secondconveyance mechanism convey the sheet increases. Accordingly, when theconveyance mechanism conveys the sheet after aligning, the sheetconveyance capability can be improved. As a result, even if the sheet isthick, a conveyance defect is less likely to occur. In addition, aconveyance delay which may be caused by a conveyance slip can besuppressed.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein maybe made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A sheet aligning mechanism comprising: a firstconveyance mechanism disposed on a first side of a sheet conveyancepath; a second conveyance mechanism disposed on a second side of thesheet conveyance path opposite to the first side, a nip being formedbetween the first and second conveyance mechanisms, wherein the firstconveyance mechanism includes a first roller, a second roller, and afirst conveyance belt wound around the first and second rollers, thefirst and second rollers configured to rotate in a first direction alonga sheet conveying direction for sheet conveyance, and stop rotation orrotate in a second direction opposite to the first direction for sheetalignment, and the first conveyance belt including an extended regionbetween the first and second rollers in an extending direction inclinedwith respect to the sheet conveying direction, such that a width of thesheet conveyance path becomes narrower towards the nip in the sheetconveying direction.
 2. The sheet aligning mechanism according to claim1, wherein the first conveyance mechanism is configured such that anangle between the extending direction and the sheet conveying directionis variable.
 3. The sheet aligning mechanism according to claim 2,further comprising: a controller configured to control the firstconveyance mechanism, such that the angle is at a first angle during thesheet alignment and then decreases to a second angle during the sheetconveyance.
 4. The sheet aligning mechanism according to claim 3,wherein the first roller is disposed upstream with respect to the secondroller in the sheet conveying direction, and movable around a rotationalaxis of the second roller to change the angle.
 5. The sheet aligningmechanism according to claim 4, wherein the first roller is a drivingroller and the second roller is a driven roller.
 6. The sheet aligningmechanism according to claim 1, wherein the second conveyance mechanismincludes a third roller, a fourth roller, and a second conveyance beltwound around the third and fourth rollers, the third and fourth rollersconfigured to rotate in a third direction along the sheet conveyingdirection for the sheet conveyance, and stop rotation or rotate in afourth direction opposite to the third direction for the sheetalignment, and the second conveyance belt including a second extendedregion between the third and fourth rollers in a second extendingdirection inclined with respect to the sheet conveying direction, suchthat the width of the sheet conveyance path becomes narrower towards thenip in the sheet conveying direction.
 7. The sheet aligning mechanismaccording to claim 6, wherein the first conveyance mechanism isconfigured such that a first approach angle between the extendingdirection and the sheet conveying direction is variable, and the secondconveyance mechanism is configured such that a second approach anglebetween the second extending direction and the sheet conveying directionis variable.
 8. The sheet aligning mechanism according to claim 7,further comprising: a controller configured to control the firstconveyance mechanism, such that the first approach angle is at a firstangle during the sheet alignment and then decreases to a second angleduring the sheet conveyance, and control the second conveyancemechanism, such that the second approach angle is at third first angleduring the sheet alignment and then decreases to a fourth angle duringthe sheet conveyance.
 9. The sheet aligning mechanism according to claim8, wherein the first approach angle and the second approach angle areindependently variable.
 10. The sheet aligning mechanism according toclaim 1, wherein the first conveyance belt includes a first portion, anda second portion disposed between the first portion and an end of thefirst conveyance belt in a width direction and having a frictioncoefficient smaller than the first portion.
 11. The sheet aligningmechanism according to claim 1, wherein the first conveyance beltincludes a first portion having a first friction coefficient and asecond portion having a second friction coefficient less than the firstfriction coefficient in a rotational direction thereof, wherein thefirst portion is positioned to corresponds to the first extended regionduring the sheet alignment.
 12. The sheet aligning mechanism accordingto claim 1, wherein the second conveyance mechanism includes a thirdroller, the nip being formed between a surface of the third roller and asurface of the first conveyance belt.
 13. An image forming apparatuscomprising: an image forming device; a sheet aligning mechanismconfigured to convey a sheet conveyed to or from the image formingdevice, the sheet aligning mechanism comprising: a first conveyancemechanism disposed on a first side of a sheet conveyance path; a secondconveyance mechanism disposed on a second side of the sheet conveyancepath opposite to the first side, a nip being formed between the firstand second conveyance mechanisms, wherein the first conveyance mechanismincludes a first roller, a second roller, and a first conveyance beltwound around the first and second rollers, the first and second rollersconfigured to rotate in a first direction along a sheet conveyingdirection for sheet conveyance, and stop rotation or rotate in a seconddirection opposite to the first direction for sheet alignment, and thefirst conveyance belt including an extended region between the first andsecond rollers in an extending direction inclined with respect to thesheet conveying direction, such that a width of the sheet conveyancepath becomes narrower towards the nip in the sheet conveying direction.14. The image forming apparatus according to claim 13, wherein the sheetaligning mechanism is configured to convey a sheet conveyed to the imageforming device.
 15. The image forming apparatus according to claim 13,wherein the sheet aligning mechanism is configured to convey a sheetconveyed from the image forming device.
 16. The image forming apparatusaccording to claim 13, wherein the second conveyance mechanism includesa third roller, a fourth roller, and a second conveyance belt woundaround the third and fourth rollers, the third and fourth rollersconfigured to rotate in a third direction along the sheet conveyingdirection for the sheet conveyance, and stop rotation or rotate in afourth direction opposite to the third direction for the sheetalignment, and the second conveyance belt including a second extendedregion between the third and fourth rollers in a second extendingdirection inclined with respect to the sheet conveying direction, suchthat the width of the sheet conveyance path becomes narrower towards thenip in the sheet conveying direction.
 17. A sheet processing apparatuscomprising: a sheet processing device configured to carry out sheetprocessing on a printed sheet conveyed from an image forming apparatus;a sheet aligning mechanism configured to convey a sheet conveyed to orfrom the sheet processing device, the sheet aligning mechanismcomprising: a first conveyance mechanism disposed on a first side of asheet conveyance path; a second conveyance mechanism disposed on asecond side of the sheet conveyance path opposite to the first side, anip being formed between the first and second conveyance mechanisms,wherein the first conveyance mechanism includes a first roller, a secondroller, and a first conveyance belt wound around the first and secondrollers, the first and second rollers configured to rotate in a firstdirection along a sheet conveying direction for sheet conveyance, andstop rotation or rotate in a second direction opposite to the firstdirection for sheet alignment, and the first conveyance belt includingan extended region between the first and second rollers in an extendingdirection inclined with respect to the sheet conveying direction, suchthat a width of the sheet conveyance path becomes narrower towards thenip in the sheet conveying direction.
 18. The sheet processing apparatusaccording to claim 17, wherein the sheet aligning mechanism isconfigured to convey a sheet conveyed to the sheet processing device.19. The sheet processing apparatus according to claim 17, wherein thesheet aligning mechanism is configured to convey a sheet conveyed fromthe sheet processing device.
 20. The sheet processing apparatusaccording to claim 17, wherein the second conveyance mechanism includesa third roller, a fourth roller, and a second conveyance belt woundaround the third and fourth rollers, the third and fourth rollersconfigured to rotate in a third direction along the sheet conveyingdirection for the sheet conveyance, and stop rotation or rotate in afourth direction opposite to the third direction for the sheetalignment, and the second conveyance belt including a second extendedregion between the third and fourth rollers in a second extendingdirection inclined with respect to the sheet conveying direction, suchthat the width of the sheet conveyance path becomes narrower towards thenip in the sheet conveying direction.